"Farmers are at higher risk of suicide any time of year for, and then over and above that there is a different risk that is related to drought," says Hanigan, who did the research as part of his PhD.

Hanigan says many have assumed drought led to higher rates in rural men, but the latest study is the first to investigate this specific link.

He and colleagues looked at the link between drought and suicide in New South Wales, which has about 600 suicide deaths per year.

The researchers compared monthly rainfall and suicide records in 11 areas across the state.

The researchers found that between 1970 and 2007 there was no link between drought and suicide rates in urban areas but a definite link in rural areas.

Most of the people studied were in the 30 to 49 age group, so the strongest conclusions were drawn from this age group.

"On average 9 per cent of suicides in rural males aged 30 to 49 is attributable to the drought index," says Hanigan.

"They are much more likely to commit suicide during a drought rather than a person in a metropolitan area."

He emphasises this is an average figure and suicides numbers are greater in drought years.

"The findings support the hypothesis that farmers and farm workers are at increased risk of suicide during droughts," says Hanigan.

Reasons unclear

But he admits the reasons why rural men are at higher risk during drought are still not clear.

Interestingly, the researchers found that suicide rates fell during drought in women in the same age group.

"That was very surprising and very noteworthy," says Hanigan.

But, he stresses that the absolute number of rural males is much larger than rural females.

"The surprising result for women reinforces the view that suicide is a very complex problem. We're only beginning to disentangle the various causal influences at work," says Hanigan.

He and colleagues are exploring the hypothesis that rural males are more at risk during a drought because they are more likely to be farmers, who depend on their natural environment more than their urban counterparts.

Hanigan says, he also wants to explore the hypothesis that rural women are less at risk because they have greater social support than men and may have "greater adaptive capacity" to the effects of drought and climate change.

"It may go some way to explaining the difference in gender results," he says.

In their study, the researchers controlled for the known long-term decline in suicide rates, and for other known effects of climate, including temperature and seasons. For example, rates are higher in spring and early summer.

If you or someone you know is thinking about suicide, call Lifeline on 13 11 14.